Electric air heater for automatic choke



2l, 196,9 Q W, CAPPELL, ET Al. 3,423,569

ELECTRIC AIR HEATER FCR AUTOMATIC cHoKE United States Patent O 3 Claims ABSTRACT F THE DISCLOSURE An electric heater for heating air passing through the automatic choke mechanism of a carburetor associated with an engine includes a resistor coil secured under tension between tubular terminals disposed at opposite ends of a tubular housing. The turns are axially spaced to allow free flow of air therebetween. The housing is sized relative to the bores in the terminal members whereby air entering the housing through one terminal may expand so that its Nelocity is reduced to allow heat to be absorbed from the resistor. Heated air leaves the housing through the other terminal. A control circuit is provided to ensure that the resistor is energized only when the ignition is turned on, the engine is running and the engine temperature is below normal.

The present invention relates to electric resistance heating elements, more particularly to elements especially adapted to warm the automatic chokes on internal combustion engines and to methods of and apparatus for controlling operation of such elements, and the principal object of the present invention is to provide new and improved methods and apparatus of the character described.

Automatic chokes, or fuel mixture enriching devices, for internal combustion engines have long employed a heat-sensitive device for automatically enriching the fuel mixture from normal when the engine is cold. As engine temperature increases with operation thereof, such device senses the increase in engine temperature and automatically ceases to enrich the mixture. While enginegenerated heat has long been employed to warm the choke device, this has not been entirely satisfactory since the choke tended to warm up too slowly thus causing excessive choking and high fuel consumption. This is a particularly acute problem in very cold weather and during short trip operation.

In order to eliminate warming of the choke device by engine-generated heat, it has been proposed to warn the choke device by means of an electric resistance heating element and in the instant invention, such element is a novel, highly simplified construction for maximum efficiency and is designed for temperature modulation by the ambient in which the engine is disposed. The present invention further porvides a novel method and apparatus for controlling operation of such heating element. These and other advantages will readily become apparent from a study of the following description and from the drawing appended hereto.

In the drawing accompanying this application and forming a part of this specification there is shown, for purpose of illustration, an embodiment which the invention may assume, and in this drawing:

FIGURE 1 is a generally diagrammatic view of the 3,423,569 Patented Jan. 21, 1969 ice invention shown in combination with an internal combustion engine of the common V type,

FIGURE 2 is an enlarged sectional view of an electric resistance heating element forming a part of the present invention, and

FIGUR-E 3 is an exploded elevational view of the element seen in FIGURiE 2 prior to iinal assembly thereof.

With reference rst to FIGURE 1, there is shown an internal combustion engine 10* of the type commonly installed in present-day motor vehicles. While engine 10 is herein shown to be of the V type, `this is illustrative only. Mounted on the usual intake manifold 11 of engine '10 is a carburetor 12 and an air cleaner 13, it being understood that air is drawn through the air cleaner and into the carburetor where the proper quantity of fuel is mixed therewith, and thereafter the fuel-air mixture is distributed to the engine cylinders by the intake manifold all in accordance with conventional practice.

yIn order to provide an enriched fuel-air mixture when starting a cold engine and during warm-up operation thereof, carburetorl 12 is provided with the usual automatic choke 14. Briefly, choke 14 comprises a housing attached to the carburetor through which a small supplv of air is drawn through a conduit 15 while the engine is operating. The housing contains a bi-metallic element which, when cold, closes a butterily valve in the carburetor to restrict air flow thereinto. When air llow through the conduit 15 has suiliciently warmed the bimetallic element, the latter opens the butterfly valve to permit unrestricted air flow into the carburetor.

The present invention, therefore, is concerned with a novel electric resistance heater 16 or heating element, for warming the air passing into the choke housing via the conduit 15 and with methods of and apparatus for controlling operation thereof as will subsequently appear.

With reference now to 'FIGURES 2 and 3, heater 16 is shown to comprise a tubular, metallic housing 17 having smaller diameter, axially spaced, tubular conductor members 18, 19 projecting axially outwardly or respective ends thereof. yExtending between members 18, 19 (see also lFIGURE 3), is a helical, resistor conductor 20, the ends of the latter being welded or otherwise suitably mechanically and electrically connected to adjoining ends of respective conductor members. lNote that the resistor conductor 20 is approximately the same diameter as the tubular members 18, 19 while the housing 17 is of considerably larger diameter to provide a radial space about the resistor conductor. To provide for anchoring the conductor member 18 to the housing 17 and for closing the adjoining housing end, member 1S has a radially enlarged ange 18.1 closely fitting within a recess 17.1 formed in the housing 17. The extreme housing end is turned radially inwardly at `17.2 to retain the member 18 in position.

At the opposite or right end of the housing, the member 19 has a radially enlarged flange 19.1; however, such flange is materially smaller in diameter than is flange 18.1 for a purpose to appear. In order to close the right end of housing 17 and simultaneously electrically insulate the member 19 from the housing, a shouldered, dielectric plug 21 is closely received within the housing. Plug 21 is provided with an annular, peripheral groove 21.1 into which the adjoining end of the housing is turned radially inwardly to secure the plug therewithin. Preferably, the right end of the housing is recessed at 3 17.3 (FIGURE 3), to reduce housing wall thickness and thus facilitate turning it radially inwardly into the plug groove.

Plug 21 is provided with a central aperture 21.2 for closely receiving the member 19 and an inwardly facing recess 21.3 for receiving the member flange 19.1. With the parts assembled as seen in FIGURE 2, the resistor conductor is under tension to insure its remaining centered within the housing and, to prevent inward movement of member 19 under the tension of the resistor, a suitable clip 22 is crimped or otherwise secured to the member 19 in abutment with the plug 21. Clip 22 may carry a suitable lug 22.1 which provides for connection of an electrical lead as will appear.

Returning now to FIGURE l, element 16 will have its tubular conductor 18 secured to the previously mentioned choke conduit so as to form a continuation thereof. The other conductor 19 will be connected to a source of clean air, such as the air cleaner 13, as by means of a rubber hose 23. Tubular conductor 18 will thus be grounded to the engine 10v while the conductor 19 will be electrically insulated therefrom. As previously mentioned, an electrical lead is adapted to be connected to the conductor 19, such lead ybeing shown at 24 as having its opposite end connected to the positive terminal 25.1 of the vehicle battery 25. The negative terminal 25.2 of the battery is grounded to the engine in the usual manner.

Interposed in the lead or circuit 24 are three switches 26, 27 and 23. Switch 26 may be the usual ignition switch which in On position provides electrical energy for operating the engine and in Off position (herein shown) terminates operation of the engine. Switch 27 may be a vacuum switch connected to the intake manifold 11 and having normally open contacts. With the engine operating, a lower than atmospheric pressure normally exists in the intake manifold and this will close the contacts of switch 27. When, however, engine operation ceases for any reason, reestablished of atmospheric pressure in the intake manifold will cause the contacts to switch 27 to reopen. Finally, switch 28 is a thermostatic switch mounted in a suitable location about the upper part of the engine where it will be subjected to the temperature of the ambient in which the engine is disposed. Switch 28 has normally closed contacts which will automatically open when temperature rises to a predetermined level.

Operation of the apparatus hereinabove disclosed will be as follows: With the engine cold and not operating, no current will be fed to the element 16 since both the switches 26 and 27 are open. If the ignition switch 26 is turned on, current will still not iiow to the element 16 since the normally open vacuum switch 27 prevents completion of the circuit 24. If the engine is now started, the lower than atmospheric pressure in the intake manifold 11 developed by the operating engine will close the contacts of switch 27 to complete the circuit 24 and energize the element 16. During energization of the element 16, current will, of course, ow through the resistor and cause it to become hot.

As the engine operates, a small ilow of air will be drawn through the element 16 and into the choke Ihousing in the conventional manner. As the air flows through the heater 16, passing in through the terminal 19, then into the housing 17, and finally out through the terminal 18, such air will be warmed by the energized resistor 20. As the resistor 20 becomes hotter, it will exert a greater warming eiect on the air passing through the element and into the choke housing to Warm the choke bimetallic spring previously mentioned.

It is an important feature of the invention that the heater housing 17 is heat-conductive; accordingly, the colder the engine environment, the slower will the element 16 heat the air passing therethrough into the choke housing. llt is also an important feature of the invention that since the cross-sectional internal size of the heater housing 17 is much greater than that of the terminals 18, 19, air velocity through such housing will be reduced to allow the air to absorb more heat from the resistor 20.

In the event the engine should stall thus interrupting air flow through the element 16, switch 27 will deenergize the element, even though the ignition remains on, to prevent possible overheating of the element. When the engine has warmed suiciently to raise the temperature of the ambient in which it is disposed to normal level, thermostatic switch 28 will deenergize the heater 16 since the air being drawn into the choke housing will now be Warm enough to keep the choke deactivated without supplemental heat from the heater,

From the foregoing it will be obvious that each time the engine cools, the cycle will be repeated upon starting the engine unless the latter has not cooled below normal operating temperature.

While the use of switches 27 and 28 has been disclosed, either one or both may be eliminated if desired. In such case, the heater 16 would remain energized at all times that the ignition switch is in on position.

In view of the foregoing it will be apparent to those skilled in the art that We have accomplished at least the principal object of our invention and it will also be apparent to those skilled in the art that the embodiment herein described may be variously changed and modified, without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described; hence it will be appreciated that the herein disclosed embodiment is illustrative only, and that our invention is not limited thereto.

We claim:

1. An electric heater for a moving fluid, comprising:

a pair of axially aligned, tubular terminal conductor members in spaced-apart relation through which the fluid to be heated may move,

a resistor conductor in the form of a helical coil whose ends are secured to respective terminal conductor members with the bore of said coil in axial alignment with the bores of the terminal conductor members, said resistor coil being tensioned between said terminal conductor members,

a tubular housing extending between said terminal conductor members and enclosing said coil, the adjoining ends of said terminal conductor members having radial enlargements for disposition at respective ends of said housing and together with said housing form a closed chamber into which fluid flows through one of said terminal conductor members and out of which fluid ows through the other of said terminal conductor members,

the diameter of the bore of said coil being substantially equal to the diameter of the bores of said terminal conductor members to maximize contact between the fluid moving through said housing and the convolutions forming said resistor coil and such convolutions being spaced axially of each other to provide free passage of ilud therebetween,

and the interior of said housing being materially larger in transverse size than said terminal conductor member bores to provide an enlarged space into which uid may expand for a reduction in its velocity.

2. The construction of claim 1, and further including switch means in electrical circuit with said resistor coil and a source of electrical energy, said switch means controlling energization of said coil.

3. The construction of claim 1 wherein said housing is metal,

wherein one of said terminal members is anchored to one housing end with its radial enlargement closing the latter,

and wherein said other terminal member extends through a dielectric bushing anchored to the other housing end.

(References on following page) 5 6 References Cited FOREIGN PATENTS UNITED STATES PATENTS 221,542 11/ 1942 Switzerland. 782,525 2/1905 Shoenberg 219--319 1,151,586 `8/ 1915 Her'kenrath 219-300 1,237,862 8/ 1917 Bintliff 219--207 X 5 ANTHONY BARTIS, Primary Examiner. 2,245,672 6/ 1944 Hunt 123-119 2,906,849 9/ 1959 Jensen et al. 219-378 U 1 3,212,486 10/ 1965 Lorge 219--207 X 'S' C X'R' 3,291,461 12/1966` Pope 123--119 12S-119; 219-207, 381; 261-39 

